New batteries store unused solar power

One of the barriers to homeowners going solar may soon be overcome, with two companies now offering home storage batteries.

The latest is a partnership between Panasonic and solar power company Solar City, offering an "affordable" solar battery storage system.

Solar City already offers to install the solar panels for free in return for a fixed monthly fee -- the problem has been storing the energy if no one is at home during the day to use it.

That lack of storage has been a hurdle for solar uptake, but now the Solar City offer includes installing a storage battery so 'free' energy produced during the day is not lost.

The battery will cost the homeowner an upfront fee of $2500 plus a monthly servicing charge.

A cross-section of the new battery (Supplied)

Solar City CEO Andrew Booth says it's about building the energy grid of the future.

"This is a real game changer for Kiwi homeowners as this smart solution will optimise their use of solar and minimise the cost of power they buy from the grid," he says.

Auckland electricity lines company Vector is also offering a home storage battery, the Powerwall, produced by electric car company Tesla.

It says it is working on ways to retrofit the battery to existing homes.

Home solar power systems are gaining in popularity. Electricity Network Association figures show 5367 solar power systems had been installed by March 2015 -- a 220 percent increase over the previous 18 months.